After all the reading this is what I understood. Is it correct?
LeaseTimeout is a simple heartbeat between SQL Server resource DLL and the SQL Server instance.
HealthCheck Timeout is related to
Why do we have two timeouts?
Also how do I change the LeaseTimeout? Is it through the cluster manager because I couldnt find any T-SQL command like below for HealthCheck Timeout
ALTER AVAILABILITY GROUP AG1 SET (HEALTH_CHECK_TIMEOUT = 40000);